diff --git a/extra/intl-extra/IntlExtension.php b/extra/intl-extra/IntlExtension.php
index 955d6ec9233..f8eaa60a91e 100644
--- a/extra/intl-extra/IntlExtension.php
+++ b/extra/intl-extra/IntlExtension.php
@@ -370,7 +370,14 @@ public function formatNumberStyle(string $style, $number, array $attrs = [], str
     public function formatDateTime(Environment $env, $date, ?string $dateFormat = 'medium', ?string $timeFormat = 'medium', string $pattern = '', $timezone = null, string $calendar = 'gregorian', string $locale = null): string
     {
         $date = twig_date_converter($env, $date, $timezone);
-        $formatter = $this->createDateFormatter($locale, $dateFormat, $timeFormat, $pattern, $date->getTimezone(), $calendar);
+
+        $formatterTimezone = $timezone;
+        if (false === $formatterTimezone) {
+            $formatterTimezone = $date->getTimezone();
+        } elseif (\is_string($formatterTimezone)) {
+            $formatterTimezone = new \DateTimeZone($timezone);
+        }
+        $formatter = $this->createDateFormatter($locale, $dateFormat, $timeFormat, $pattern, $formatterTimezone, $calendar);
 
         if (false === $ret = $formatter->format($date)) {
             throw new RuntimeError('Unable to format the given date.');
@@ -397,7 +404,7 @@ public function formatTime(Environment $env, $date, ?string $timeFormat = 'mediu
         return $this->formatDateTime($env, $date, 'none', $timeFormat, $pattern, $timezone, $calendar, $locale);
     }
 
-    private function createDateFormatter(?string $locale, ?string $dateFormat, ?string $timeFormat, string $pattern, \DateTimeZone $timezone, string $calendar): \IntlDateFormatter
+    private function createDateFormatter(?string $locale, ?string $dateFormat, ?string $timeFormat, string $pattern, ?\DateTimeZone $timezone, string $calendar): \IntlDateFormatter
     {
         $dateFormats = self::availableDateFormats();
 
@@ -410,7 +417,10 @@ private function createDateFormatter(?string $locale, ?string $dateFormat, ?stri
         }
 
         if (null === $locale) {
-            $locale = \Locale::getDefault();
+            if ($this->dateFormatterPrototype) {
+                $locale = $this->dateFormatterPrototype->getLocale();
+            }
+            $locale = $locale ?: \Locale::getDefault();
         }
 
         $calendar = 'gregorian' === $calendar ? \IntlDateFormatter::GREGORIAN : \IntlDateFormatter::TRADITIONAL;
@@ -421,12 +431,14 @@ private function createDateFormatter(?string $locale, ?string $dateFormat, ?stri
         if ($this->dateFormatterPrototype) {
             $dateFormatValue = $dateFormatValue ?: $this->dateFormatterPrototype->getDateType();
             $timeFormatValue = $timeFormatValue ?: $this->dateFormatterPrototype->getTimeType();
-            $timezone = $timezone ?: $this->dateFormatterPrototype->getTimeType();
+            $timezone = $timezone ?: $this->dateFormatterPrototype->getTimeZone()->toDateTimeZone();
             $calendar = $calendar ?: $this->dateFormatterPrototype->getCalendar();
             $pattern = $pattern ?: $this->dateFormatterPrototype->getPattern();
         }
 
-        $hash = $locale.'|'.$dateFormatValue.'|'.$timeFormatValue.'|'.$timezone->getName().'|'.$calendar.'|'.$pattern;
+        $timezoneName = $timezone ? $timezone->getName() : '(none)';
+
+        $hash = $locale.'|'.$dateFormatValue.'|'.$timeFormatValue.'|'.$timezoneName.'|'.$calendar.'|'.$pattern;
 
         if (!isset($this->dateFormatters[$hash])) {
             $this->dateFormatters[$hash] = new \IntlDateFormatter($locale, $dateFormatValue, $timeFormatValue, $timezone, $calendar, $pattern);
diff --git a/extra/intl-extra/Tests/IntlExtensionTest.php b/extra/intl-extra/Tests/IntlExtensionTest.php
index f2637620693..a05f796f914 100644
--- a/extra/intl-extra/Tests/IntlExtensionTest.php
+++ b/extra/intl-extra/Tests/IntlExtensionTest.php
@@ -12,17 +12,56 @@
 namespace Twig\Extra\Intl\Tests;
 
 use PHPUnit\Framework\TestCase;
+use Twig\Environment;
 use Twig\Extra\Intl\IntlExtension;
+use Twig\Loader\ArrayLoader;
 
 class IntlExtensionTest extends TestCase
 {
+    public function testFormatterWithoutProto()
+    {
+        $ext = new IntlExtension();
+        $env = new Environment(new ArrayLoader());
+
+        $this->assertSame('12.346', $ext->formatNumber('12.3456'));
+        $this->assertSame(
+            'Feb 20, 2020, 1:37:00 PM',
+            $ext->formatDateTime($env, new \DateTime('2020-02-20T13:37:00+00:00'))
+        );
+    }
+
     public function testFormatterProto()
     {
-        $dateFormatterProto = new \IntlDateFormatter('fr', \IntlDateFormatter::FULL, \IntlDateFormatter::FULL);
+        $dateFormatterProto = new \IntlDateFormatter('fr', \IntlDateFormatter::FULL, \IntlDateFormatter::FULL, new \DateTimeZone('Europe/Paris'));
         $numberFormatterProto = new \NumberFormatter('fr', \NumberFormatter::DECIMAL);
         $numberFormatterProto->setTextAttribute(\NumberFormatter::POSITIVE_PREFIX, '++');
         $numberFormatterProto->setAttribute(\NumberFormatter::FRACTION_DIGITS, 1);
         $ext = new IntlExtension($dateFormatterProto, $numberFormatterProto);
+        $env = new Environment(new ArrayLoader());
+
         $this->assertSame('++12,3', $ext->formatNumber('12.3456'));
+        $this->assertSame(
+            'jeudi 20 février 2020 à 14:37:00 heure normale d’Europe centrale',
+            $ext->formatDateTime($env, new \DateTime('2020-02-20T13:37:00+00:00'))
+        );
+    }
+
+    public function testFormatterOverridenProto()
+    {
+        $dateFormatterProto = new \IntlDateFormatter('fr', \IntlDateFormatter::FULL, \IntlDateFormatter::FULL, new \DateTimeZone('Europe/Paris'));
+        $numberFormatterProto = new \NumberFormatter('fr', \NumberFormatter::DECIMAL);
+        $numberFormatterProto->setTextAttribute(\NumberFormatter::POSITIVE_PREFIX, '++');
+        $numberFormatterProto->setAttribute(\NumberFormatter::FRACTION_DIGITS, 1);
+        $ext = new IntlExtension($dateFormatterProto, $numberFormatterProto);
+        $env = new Environment(new ArrayLoader());
+
+        $this->assertSame(
+            'twelve point three',
+            $ext->formatNumber('12.3456', [], 'spellout', 'default', 'en_US')
+        );
+        $this->assertSame(
+            '2020-02-20 13:37:00',
+            $ext->formatDateTime($env, new \DateTime('2020-02-20T13:37:00+00:00'), 'short', 'short', 'yyyy-MM-dd HH:mm:ss', 'UTC', 'gregorian', 'en_US')
+        );
     }
 }